TALLAHASSEE -- Lawmakers advanced changes to Florida's controversial "stand your ground" law Tuesday in the wake of the George Zimmerman trial and a summer of protests after his acquittal in the shooting death of Trayvon Martin.

But gun-rights groups and several Republican lawmakers on a Senate panel that passed the changes expressed doubts about its extension of legal liability to people acting in self-defense when they negligently injure or kill an innocent bystander in the process.

That was one of several recommendations that came out of task force appointed by Gov. Rick Scott last year following the Martin shooting. But Sen. John Thrasher, R-St. Augustine, said he didn't think the change was necessary and voted against the bill, along with Sen. Rob Bradley, R-Fleming Island.

"What we're saying is we're putting them in jeopardy even if they're trying to defend themselves," Thrasher said.

The lawmaker largely responsible for drafting the 2005 law -- allowing citizens to use deadly force without trying to retreat when they felt their lives were in danger -- opened the two-hour hearing Tuesday with a defense of it.

"Florida's Stand Your Ground law has been the subject of intense public debate and scrutiny," Sen. David Simmons, R-Altamonte Springs, told the Senate Judiciary Committee, which passed the bill, 7-2.

"I think everyone has found it is an excellent, common sense law. But it is not perfect."

But Simmons also served on the task force and defended the need to protect innocent bystanders in cases where someone might spray bullets in the air or otherwise act with "negligence."

Simmons' bill, (SB 130) is being combined with similar legislation (SB 122) sponsored by Senate Minority Leader Chris Smith, D-Fort Lauderdale, although the two still have differences over how much protection to provide for people who use deadly force. Those differences, they said, would be worked out later.

"This has truly been an effort in which we have taken this issue, dealt with it in a bipartisan constructive manner and I believe reached a consensus thus far," Simmons said.

The legislation slated for a vote today is inspired by some problems exposed in the Trayvon Martin case. It would require county sheriffs and city police departments to set guidelines for "neighborhood watch" programs like the one to which Zimmerman belonged, and to restrict their activities to observing and reporting suspected crimes.

Zimmerman said he followed Trayvon Martin as the teen walked back to the condo where his father was staying. The two confronted one another, with fatal results.

The Florida Sheriffs Association, however, has expressed problems with one idea in the bill to require teaching materials for additional training for such watch programs. Simmons told the panel he would likely back off that requirement, and allow law enforcement to develop their own guidelines.

"After what happened in Sanford we want to send a message to neighborhood watch programs ... about what is acceptable behavior," Smith said.

As recommended by the task force Scott named last year to review the law, the bill would also prohibit people who are the "aggressors" in confrontations from then claiming "stand your ground" immunity. And it would specify that law enforcement must still conduct a full investigation in shootings where the law is being claimed as a defense -- another change spurred by the law enforcement claim that it couldn't do so in the Zimmerman case.

Critics of the Florida law say the fixes so far don't do enough.

Smith wants a broader definition of "aggressors" and for the state to track the use of the law statewide to get better data than the anecdotal cases collected so far.

Another debate is over what constitutes "unlawful activity" in which the immunity protection of the law would not apply. Simmons told the panel Tuesday he felt that cases in which someone was simply an illegal immigrant or "jaywalking" should not be considered "unlawful," although the law currently is ambiguous about that. The bill currently dosn't address that issue, although Senate Judiciary Chairman Tom Lee, R-Brandon, said it should.

"We're here today because we disagree, but we're not afraid to discuss," Smith told the panel. "I support what we're doing today because I think it's important to the state of Florida."

In the House, Reps. Dennis Baxley, R-Ocala, and Bruce Antone, D-Orlando, are expected to carry similar bills, although Rep. Alan Williams, D-Tallahassee, has also filed a bill to repeal 'stand your ground' entirely.

U.S. Attorney General Eric Holder made an impassioned call this week to overturn "stand your ground" laws in states across the nation in the wake of George Zimmerman's acquittal in Trayvon Martin's shooting death.

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